The state Oil and Gas Conservation Commission approved Monday new groundwater protection rules that it said were among the strongest in the nation, though both industry and environmental interests said they were unhappy with the regulations.

The new rules require that operators sample nearby water wells before and after drilling activities to ensure that oil and natural-gas development does not harm water supplies and to identify potential problems.

“This new set of groundwater monitoring rules once again puts Colorado in the forefront of thoughtful and progressive regulatory oversight of energy development,” commission Director Matt Lepore said in a statement. “We worked earnestly with many stakeholders to develop a groundwater rule that provides strong protections and that we believe strikes the right balance among many interested parties.”

Only two other states have mandatory groundwater programs in place, according to the commission. No other state requires operators to collect water samples after drilling.

Colorado’s rules will require sampling as many as four water wells within one-half mile of a new oil and gas well before drilling. Two more samples of each well must be taken between six and 12 months and again between five and six years, a requirement the commission called “unprecedented among other states.”

The Colorado Oil and Gas Association, an industry lobbying group, criticized the new standards.

“The Colorado Oil & Gas Association supports a statewide groundwater baseline sampling program that continues Colorado’s leadership as a state balancing responsible energy development with environmental stewardship,” Doug Flanders, the association’s director of policy, said in a statement. “Unfortunately, this new rules does not seem to meet that balance.”

Flanders called the new rules “excessive and unnecessary.” He said the state instead should continue a year-long voluntary groundwater monitoring program in which operators who drilled more than 93 percent of Colorado’s wells participated.

“If this program would have been converted to a mandatory program, it would have been one of the most comprehensive water programs in the country, significantly exceeding many other water sampling requirements in the country in both scientific rigor and transparency,” Flanders said.

The New York City-based Environmental Defense Fund called the standards “the weakest rule in the nation for testing groundwater around oil and gas operations.”

Dan Grossman, the environmental group’s Rocky Mountain regional director and a former Colorado lawmaker, said the rules cap the number of water sources operators must sample within a well radius. That allows companies to “cherry pick” wells they want to test. It also makes Colorado the first of five states that have proposed or adopted groundwater testing programs to place an “arbitrary” cap on which water wells undergo testing.

“At a time when Colorado desperately needs a signal that state officials are listening to the concerns of citizens and communities, it is unfortunate that the administration failed to adopt a rigorous, science-based program to adequately assess whether our groundwater is being protected,” Grossman said.

In the Greater Wattenberg Area in Northern Colorado, operators will be required to sample one water well per quarter section before and after drilling. The rule is more relaxed in the zone because of the combination of energy development, agriculture and other industrial and residential uses there, according to the commission.

Grossman called the exemption of the zone a “massive carve-out for the area with the most intensive drilling activity — precisely the area that demands the greatest scrutiny, not the least.”

Approval of the rules follows months of discussions aimed at crafting regulations that suit both water-well owners and the oil industry, the state said.

“We have listened carefully and considered the views of many parties, including many citizens,” commission chairman Tom Compton said in a statement. “We believe this rule gets us to a result that rigorously protects the environment while addressing and incorporating the varied concerns of numerous interests.”

The commission will spend the next two days hearing testimony as it considers new rules on distances between drilling operations and occupied buildings.